Passenger Car Investigations of NOx-Adsorber and DPF Combination to Fulfill Future Diesel Emission Limits

The current study focuses on the operating behavior of a NO_x-adsorber catalyst upstream of a Diesel particulate filter as two separate exhaust gas aftertreatment components. New European drive cycle (NEDC), US FTP 75, and US06 tests with a NO_x-adsorber have been performed with and without a DPF in two passenger cars with initial test weights (ITW) between 1550 and 1750 kg. Transient particle size distributions have also been measured during FTP 75 and US06 tests. Also on road driving with a NO_x-adsorber and DPF has been carried out. During these tests, the focus has been on the NO_x-adsorber catalyst and on the interaction between the NO_x-adsorber and the DPF. The purge events to regenerate the NO_x-adsorber (rich exhaust gas composition,λ < 1) have been controlled automatically via new engine control unit functionalities. These algorithms have been developed using the rapid prototype tool ETAS ASCET. Exhaust gas back pressure behavior as well as timing and efficiency of DeNO_x-purge events over driving distance and during different driving conditions have been investigated and the oil dilution as a consequence of regeneration of NO_x-adsorber (DeNO_x-purge) has been evaluated. NO_x conversion efficiency depends on driving patterns and optimization of the corresponding control functions. Overall, a potential for NO_x reduction above 50% during real world driving has been observed with unexpected low DPF back pressure increase.